Corona-poled piezoelectric polymer layers of P(VDF/TrFE) for micromachined silicon microphones

Abstract
In this paper a non-traditional, but IC-compatible fabrication technology for micromachined acoustical silicon sensors for airborne sound is described. The microphones are based on the piezoelectric effect of P(VDF/TrFE)-layers, which are placed on top of a very thin silicon nitride membrane (area: 1 mm2). The P(VDF/TrFE)-layers are spin-coated, annealed and poled by corona discharge, in order to get piezoelectric behaviour. As a result of the design and the technology process, a maximum sensitivity of 150 mu V Pa-1, a bandwidth of about 16 kHz and an equivalent noise level of less than 60 dB(A) were measured. These values are much better in comparison to those measured at former silicon microphones with piezoelectric polymer layers.

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